


Uncertainty Principle

by scratchienails



Category: Dr. STONE (Anime), Dr. STONE (Manga)
Genre: Birthday Fluff, Can Love Bloom In the Stone Age?, Canon Compliant, Character Study, Established Relationship, Fluff, Gift Giving, M/M, Spoilers, Yeah I don't know how to tag this, based on a Tumblr idea, hinted at - Freeform, mostly - Freeform
Language: English
Status: Completed
Published: 2019-10-07
Updated: 2019-10-07
Packaged: 2020-11-26 16:29:29
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,711
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20933270
Author URL: https://archiveofourown.org/users/scratchienails/pseuds/scratchienails
Summary: Senku was ten billion percent sure he’d fallen, hook, line and sinker, for another one of Gen’s tricks.In his personal defense, it hadn’t been obviously a ploy at first.





	Uncertainty Principle

**Author's Note:**

> Based on [this idea/theory](https://thesublimeiseverywhere.tumblr.com/post/187753685641/tarot-gen-cards-a-conspiracy-theory-and-hcs). Probably doesn't match all the details of the manga, but I got lazy! Enjoy my nonsense, this is all such self-indulgent silliness!

Since arriving at Ishigami Village, his days had been busy. There was always something more that needed to be done, and more often than not, that something was tedious and time-consuming. By itself, that was hardly new: since the moment he’d awoken in this changed world, every step he wanted to take forward was painstaking. Nothing was as easy or simple as it had been before, but now he had an entire village to look out for and the omnipresent threat of Tsukasa looming over his head.

The nights, however, were calm. Though they had electricity and lightbulbs now, there was no justification to wasting such precious and hard-won resources on staying up all night. Torchlight only got so far, and as such, as the sun went down, he had gotten in the habit of retiring with it.

Except for the nights he stayed up and watched the stars from his observatory. Nights like tonight, when the sky was cloudless and clear and the whole Milky Way spilled across the sky before him.

He heard footfalls, quiet as a cat and just as lethargic, and tore his eyes from the sky to see a shadow entering. 

“The stars are clearer than they used to be.” Gen said, by way of greeting, as he placed a tray of tea down. The steam wafting off the ceramic cups rose towards the violet of the night sky, and Senku’s eyes followed it, not needing to look to know the relaxed smile no doubt pulling at Gen’s lips. 

The night sky was more brilliant than it ever was to their eyes before. 

Senku grew up with a black canvas speckled with little pinpricks of light and hazed with yellow, but what hung over his head was a tapestry of blues and purples and misty gray, filled with so many stars that it seemed as if they might overflow and come tumbling down from the heavens.

Of course, that was impossible. The closest known phenomenon would be a meteor shower, or maybe a supernova. In the thousands of years that had passed them by, it wasn’t impossible that one of the stars they’d been familiar with revealed itself to be destructing. Now that he had a telescope—however rudimentary and (metaphorically) begging for some modern upgrades it was—he could even check. 

Not that he didn’t already have enough on his plate, ha. 

Well, it was the telescope Gen had made for him; it wouldn’t be right to just take it apart and upgrade it right out of existence by replacing its every part with refined improvements. No, it would be better to keep the telescope as it was and make a new one from scratch: it was, technically, the first telescope of the new age, after all. That certainly made it a worthy souvenir of some sort, and it could tide him over until he had the spare time and materials for spoiling himself. 

He took a cup of tea, feeling the burn of heat against his hands. Gen’s eyes were still on the sky, the silvery moonlight cascading over his face and shining in his ivory hair. 

White and black, just like the moon and the night. Someday, Senku would find the time to waste on figuring out that too.

“Light pollution hid most of galaxy from view back in our day.” He said, remembering the nostalgic yellow glow. He had nothing but admiration for Edison, Tesla, and all others involved, but he knew progress always had a cost: though humanity had fought off the darkness, they’d paid with all but the brightest stars.

“If we bring civilization back, we won’t be able to see this view anymore, huh?”

A small price to pay for safe cities and banished darkness. He hadn’t been exaggerating when he spoke to Chrome about the wonders of electric lights. Still he hummed his agreement. “If we can’t see it from down here, we’ll just have to go higher.”

“You mean you’re still going to the moon?” Gen laughed a little, and Senku couldn’t stop his own smile even if he tried. “Isn’t all this already enough adventure for you, Senku-chan?”

No, it could never be enough, not while there was still the entire cosmos out there, filled with so many unknowns. They both knew that.

For a moment, they lapsed into silence. As the moon trekked over the sky, he found himself lounging back, fondly watching his old friend move with half-lidded eyes. Gen remained seated, knees bent under him and feet poised, his posture polite and straight and well-practiced. If Senku didn’t know so much, he could have been fooled into thinking Gen was a proper young master, ready for a tea ceremony.

Absurd.

“Now that we have paper,” Gen spoke eventually, rotating his cup in hand and taking long, elegant sips, “we should make a proper calendar, don’t you think?”

Senku peeked at him, lazily, not quite willing to expend the energy needed to lift his eyelids all the way. Gen smiled back, his face completely lax.

In hindsight, _that _look had undoubtedly been what tricked him at first: that expression hadn’t given him a single hint that Gen was up to no good.

In his defense, it was a reasonable suggestion. Even then, he was still counting the seconds, tracking the days, even going so far as to calculate the exact amount of time he spent asleep so he could keep the timing accurate.

Truthfully, Senku couldn’t really imagine life without it, not anymore, but if they had a calendar…

It would be a step towards letting those three thousand and six hundred and eighty-nine years go, wouldn’t it? A step towards living in the moment, the present, once more, without feeling like he was a ticking clock disconnected with reality.

“That’s not a bad idea.” Another smile crept over his lips, mirroring the perfect curve of Gen’s lips.

The next morning, Senku brought the concept to their resident artist, Gen lethargically trailing at his heels with his hands buried in his sleeves. Ishigami Village already had a concept of tracking days and months, but it was Spartan and based on moon cycles, not the months he and Gen were more familiar with. It served the purpose of tracking the seasons and the single holiday of the village well enough, but concepts like the leap year and the shifting number of days to the months was beyond it.

What he didn’t remember perfectly, he had to calculate: what day was it? He knew the number by heart, the date and the time, but figuring out whether it was a Tuesday or a Thursday or etc was another matter entirely.

From there, it was easy to draw up a prototype and let Gen fill in the details.

“This is Christmas, this is Children’s Day, Valentine’s, White Day, New Years...” For a moment, he let himself get caught up in the rise and fall of Gen’s voice, watching slim fingers point out little boxes. Gen’s hands were rougher than they used to be: Senku’s own were calloused and worn in ways they’d never been before, but Gen’s maintained a sort of elegance and dexterity despite the hard conditions. He liked watching them move, gliding over pressed paper like it was laminated. “We should do birthdays as well…see, this one is Senku-chan’s, and this one is mine—“

Their artist and many others in the village couldn’t read or write yet, so they settled for little caricatures marking the important days.

And if his eyes lingered on the little impression of Gen sketched: fox-faced with sly eyes and a slyer mouth, no one needed to ever know.

It stuck with him.

Gen gave away his birthday so easily, with Senku _right_ there, and this must have been a trap. It had to have to been on purpose. Gen wanted gifts, obviously, and Senku was probably going to have to do better than a bottle of Cola.

Well, all _was_ fair in love and war.

A magician’s toolbox was almost as extensive as a mechanic’s, but infinitely more mysterious. Despite his limited resources, Gen had filled his rather well.

Senku watched as Gen dressed one morning, watching as Gen slipped into each layer and repacked his supplies. The top layer, the long coat, was the most extensive: almost entirely lined with sachets and pockets and packages Senku hadn’t had the liberty to investigate yet. But the layers underneath were no less impressive, with fake blood and flowers and handkerchiefs and so much more.

Some of Senku’s own tools worked their way in as well, over the months. It was more convenient for Gen to carry some things, like sealed beakers of chemicals and samples, scalpels, and gun powder. It was a simple matter of logistics: he was more agile and graceful than Senku, and therefore, far less likely to trip and fall and break their painstakingly crafted glassware.

Most of all, however, Senku paid close attention to what was _not_ there.

The most egregious of which was cards.

Every magician needed at least one pack of cards, but Gen had none.

The artist eyed him suspiciously. “No Gen?”

Gen and he were not inseparable. Not entirely. It was just natural to keep Gen close, considering the magician’s nature, and it was a matter of practicality too. At first, Gen was the only other citizen of the Kingdom of Science that remembered the modern world, the only person that truly grasped the concepts with which Senku spoke and understood the vision behind them.

That sort of companionship was a rarity in the time of grand bouts and foxtails, and though he wouldn’t trade Chrome and Kaseki for the world, they just didn’t _get_ it all in the same way he and Gen could.

But that didn’t mean Senku couldn’t go anywhere on his own.

“Gen’s with Suika, gathering supplies.” Senku waved off. “Care to help me with a little project?”

It was a relatively simple undertaking compared to constructing an entire observatory, but the concept behind it, Senku felt, was somewhat comparable. Gen gave him back not only a great tool, but something that was almost essential to his identity. Like the day his father bought him everything he needed to start his journey to space, Gen gave him back the stars and moon he loved so much.

Now, he could give Gen back something he’d lost as well. Much smaller, yes, but no less precious. He could picture in his mind a younger Gen struggling with a deck of cards, trying to get his fingers and the slick paper to work in perfect tandem, practicing for months and years and always bursting to learn the next mind-blowing trick.

No point in letting such a carefully cultivated skill go to waste. And knowing Gen, he’d put his tricks to good use without prompting, in that stunningly resourceful way of his.

But, the cards being a solid investment aside, Gen had been so bold in asking for a birthday present when he set it all up like that. Completely and utterly shameless.

Senku couldn’t help but want to make him sweat, just a little. 

“Pine trees? I know a grove.” Ukyo said, raising an eyebrow. “But we already have plenty of wood.”

“I need pine resin. A lot of it.”

It had been some time since the merge with the Empire of Might, but still some issues remained. Despite all the stress, and the expansion, and the endless march forward, Gen’s birthday was creeping towards him with each day. There was just as much to do as there had ever been, even with the truce, but still he found moments to steal away for his little side project.

Ukyo seemed a little curious, but was more than willing to help Chrome and him collect the necessary resin.

Between the three of them, Senku had far more gathered than he needed in no time at all. It was hardly a waste: turpentine was a useful solvent to have on hand anyway. The distilling process took more time, and far more tries too, but he eventually got the hang of it.

But even Chrome and Ukyo struggled to find any American black walnut trees. He would just have to settle for the native Japanese walnuts. It wasn’t ideal, but at the same time, he wasn’t certain how much of a difference it would even make.

The recipe was simple, even if he’d never tried his hand at it before: soot, turpentine, walnut oil. He experimented with the combinations a bit, testing and testing until he had just the right consistency and color. Or at least what seemed sufficient.

Normally, trial and error didn’t make him feel so self-conscious, but something about watching the handmade ink dry splotchy and unappealing almost made him want to give it up entirely.

If Gen was going to have cards, Senku wanted them to be _nice_ cards.

The red ink was even more difficult, since he didn’t want it to smudge. The best option, he figured, would be red India ink, but even he only knew how to make India ink in black. In the end, he improvised with the turpentine and walnut oil again, only this time, he added berries in the place of soot. The result wasn’t the vivid red of modern playing cards, but it dried well without being too brown.

There was that itchy, uncomfortable feeling again. It wasn’t something he usually associated with Gen; if anything, Gen had a way of making Senku feel certain and assured. He was confident by nature, mentalist or not, but Gen could always tell when he was unsure. There would be no hiding it from a skilled actor, and certainly no fooling a psychologist; trying to hide his faltering surety was a fool’s errand.

And Gen knew how to make him feel better: by either solving the problem entirely, or at least giving Senku a chance to take his mind off it.

Were some shoddily painted pieces of paper really enough, in the face of that?

He was overthinking it, he decided later, looking through the lens of history’s worst telescope.

Gen didn’t even wear _shoes_. He had no standards.

Methodical, step by step, one ingredient obtained after another, that was the life Senku lived now. Grinding forward, without ever stopping.

But he didn’t have to grind alone.

There were a lot of them now, well over a hundred, and that meant plenty of birthdays had come and gone. And each time Gen dragged him to the party, that sly glint in his dark eyes.

Yeah, Senku really wanted to mess with him.

If he was going to make a pack of cards, it might as well be a pack befitting the Science Kingdom. Tarot cards for the mentalist, poker cards for the magician, and flashcards for Senku’s right hand man to finally learn some decent science.

He assigned each suit a discipline: biology, chemistry, physics, and mathematics. The difficulty of each concept rose with the number, starting simple and gaining increased complexity. From the order of operations to infinitesimals, from gravity to quantum field theory.

Their artist drew a slash down each Joker’s face, perfectly capturing the crack in Gen’s upturned cheek. The Joker, Senku thought, encapsulated Gen remarkably well. The trickster, the wild card, the supposedly malicious odd one out. In as neat lettering as he could manage, he placed ‘Uncertainty Principle’ upon it, and failed to not smile at his own little joke.

Duplicitous, both particle and wave: it was impossible to know just where he stood or where he would be next, or how fast he would end up there, just the strong probability that he would be by Senku’s side.

Yes, it all suited Gen just fine.

Gen’s birthday snuck up on them quietly, much like the man himself, but Gen made sure they all saw it coming regardless. Swindling people was child’s play for him, so subtly pressing into their heads what he wanted from them each? As easy as breathing.

With those sneaky, expectant eyes upon him, Senku took a little too much satisfaction in showing up to the party empty-handed. Kohaku nearly broke his ribs with her elbow, but it was worth it to see the concealed shock struggling to break through Gen’s poker face.

“That’s cold, Senku-chan.” Gen pouted, but behind the sulky look was a glint of calculation.

“It’s what you deserve, you sneaky bastard. You set me up.”

Gen whistled innocently. “And you had your fun. Where’s my gift?”

“Dunno, did you get yourself one?” Senku glanced his way, a teasing smile pulling at his lips. “Maybe try playing the party game?”

The party game turned out to be, surprise surprise, a riddle-based treasure hunt.

Yeah, Senku came up with the hints himself. It had only taken him an entire night or two. No big deal.

Twenty-one riddles later, everyone at the party hated him and Gen had finally realized that some of the blood packages in his coat had been replaced with the prize.

“You’re terrible, Senku-chan!” He wailed. “You hid the prize on me the whole time?”

It hadn’t been easy: Gen knew his materials well, and would have noticed any tampering with just about any of them, but a deck of cards wasn’t all the different in size and weight than the padding behind his blood packs. Switching them out hadn't been easy, but he wasn't one to back off from a challenge.

Senku was just a little bit smug about pulling it off.

“What is it? What is it?” Suika was chirping, bouncing up and down to get a better look at the packages in Gen’s hands. At her behest, he dropped the dramatics and began to unwrap. Everyone’s eyes were on his hands and the gifts, but Senku’s stayed on his face, watching with rapt fascination at the stuttering of Gen’s expression, the almost misty look in his eyes, the slight quiver of his almost eternally steady hands.

“Paper?” Kohaku exclaimed, right before she attempted to shake Senku’s brains rights out of his skull. “You put us through all that for some paper?!”

It was totally worth seeing the reverent way Gen’s fingers curled around each deck of cards, the way he flipped through them like he’d held them a billion times before, the way he eventually smiled: wide and fierce and bursting.

A billion percent worth it.

Before he knew it, they were on a ship together, once more staring up at the sky. This time, however, he thought of the silly books Gen used to write, and the silly questions that hid inside.

Senku had his own silly questions.

“Hey, if you were on a trip to space, who would you take with you?”

Gen peered at him, all sly-eyed and gleaming. “That sounds like a loaded question, Senku-chan.” His voice, a weapon just as much as Kohaku’s sword, was soft and clear in the night air. Senku could imagine the words curling at their edges, warmed by good humor. “Are you asking who I think would be best, or who I like best?”

“No one ever gives me a straight answer to that question.”

“Well, then who would Senku-chan take, hm?” Gen hummed. “Yuzuriha-chan and Taiju-chan?”

Once upon a time, Senku’s answer would have been that simple. But the people his father went with to space were the only ones he got to keep, the ones that lived and died by his side in an empty world.

It wasn’t so much a question of who he’d take with him, but rather, who he could bear to leave behind.

Feeling a little helpless, he grinned. “I guess I’d find a way to take everyone.”

“That’s ridiculous!” Gen exclaimed, waving a hand. “It’s not like loading us all onto this ship. There’s no rocket that can take everyone to space!”

“Then I’ll build one.” Senku pinched his chin, unable to _not_ start the blueprints unfurling in his head at just the idea. “And I’ll take the Kingdom of Science with me to the moon on it.”

Gen’s eyes were on him, no longer surprised, but glittering with _something _anyway.

It was a look Senku never really knew what to do with, but made him feel like puffing out his chest anyway, like he’d done something right or said something particularly clever. Like he’d aced some test he hadn’t realized he’d been taking.

Turn-about was fair play, though. “Come on, haven’t you ever wanted to be an astronaut? Go to space?”

Gen smiled, slow and a little teasing. “Not everyone’s you.” Fair enough. Gen’s childhood dreams probably had more to do with fame and fortune than moon rocks and zero gravity. “Don’t astronauts have to go through all sorts of training and tests? I think I’ll pass.”

Senku couldn’t help but chuckle, feeling a little devilish at the thought of poor, graceful Gen being put through something like an aerotrim or a centrifuge. “Then who’s going to negotiate with the aliens we meet?”

“Nobody. There aren’t going to be any aliens to negotiate with.” Gen rolled his eyes. “Not on the moon.”

“We don’t know that. It’s been over 3,700 years since humans were last there.”

“Alright, and what if these hypothetical aliens are the real source of the petrification?”

“Well, then I’ll really need my mentalist with me, won’t I? That sounds like a rough grounds for negotiation without him.”

“Just because I came along on this trip across the globe for you doesn’t mean I’m willing to leave said globe for you.”

“Like you aren’t over the moon for me already?”

The joke was stupid and cheesy, but Gen’s eyes were shining in the moonlight and Senku might just be the one that was already over the moon.

Because, in the end, there was no guarantee they’d get there. But for all the uncertain things in the world, there was one thing Senku knew for sure: where he went, Gen would follow. To give him gifts, to carry his beakers, to needle him for Cola and cards.

Wherever they ended up, they’d get there together, no matter what the Uncertainty Principle said.

And that was more than enough.


End file.
